In general, an electrostatic atmosphere is made in a refrigerator, and meats and fishes are thawed in the refrigerator at a minus temperature. In addition, fruits are kept fresh in the refrigerator.
This technology uses supercooling. Supercooling means that a molten object or a solid cooled below a phase transition temperature in a balanced state is not changed.
This technology is mentioned in Korea Laid-Open Patent Official Gazette 2000-0011081 disclosing an electrostatic field processing method, an electrostatic field processing apparatus, and electrodes therefor.
FIG. 1 is a structure view illustrating a conventional apparatus for thawing and freshness keeping. A cooling device 1 includes an insulation 2 and an outer wall 5. A temperature control device (not shown) is installed in the cooling device 1. A metal shelf 7 installed in the cooling device 1 has a two layer structure. Vegetables, meats or marine products are mounted on each layer for thawing, freshness keeping or ripening. The metal shelf 7 is isolated from the bottom of the cooling device 1 by insulators 9. A high voltage generating device 3 can generate 0 to 5000V of DC and AC voltages. The inner surface of the insulation 2 is covered with an insulating plate 2a such as vinyl chloride. A high voltage cable 4 for outputting the voltage of the high voltage generating device 3 accesses the metal shelf 7 through the outer wall 5 and the insulation 2.
When the user opens a door installed on the front surface of the cooling device 1, a safety switch 13 (refer to FIG. 2) is turned off to block the output of the high voltage generating device 3.
FIG. 2 is a circuit view illustrating the high voltage generating device 3. 100V of AC is supplied to a primary side of a voltage adjusting transformer 15. Reference numeral 11 denotes a power lamp and 19 denotes an operation state lamp. When the door 6 is closed and the safety switch 13 is on, a relay 14 is operated. The operation of the relay 14 is displayed by a relay operation lamp 12. Relay contact points 14a, 14b and 14c are closed by the operation of the relay 14, and 100V of AC is applied to the primary side of the voltage adjusting transformer 15.
The applied voltage is adjusted by an adjusting knob 15a at a secondary side of the voltage adjusting transformer 15. The adjusted voltage is displayed on a voltmeter. The adjusting knob 15a is connected to a primary side of a boosting transformer 17 at the secondary side of the voltage adjusting transformer 15. The boosting transformer 17 boosts a voltage at a rate of 1:50. For example, when 60V of voltage is applied, it is boosted to 3000V.
One end O1 of the secondary side output of the boosting transformer 17 is connected to the metal shelf 7 isolated from the cooling device 1 through the high voltage cable 4, and the other end O2 of the output is grounded. Since the outer wall 5 is grounded, if the user contacts the outer wall 5 of the cooling device 1, he/she does not receive an electric shock. In FIG. 1, the metal shelf 7 exposed in the cooling device 1 must be maintained in an insulated state. It is thus necessary to separate the metal shelf 7 from the walls of the cooling device 1 (the air performs insulation). If the contents 8 mounted on the metal shelf 7 contact the walls of the cooling device 1, the current flows to the ground through the walls of the cooling device 1. Drop of the applied voltage is prevented by adhering the insulating plate 2a to the inner walls. When the metal shelf 7 is not exposed but covered with vinyl chloride, an electric field atmosphere is made in the whole cooling device 1.
The conventional cooling device 1 controls only the magnitude of the voltage applied to the metal shelf 7 to supercool the foods. Accordingly, supercooling occurs at −5° C., to prevent freezing of the foods. In the case that the magnitude of the voltage is varied, a minimum temperature for generating supercooling is −5° C. The foods cannot be supercooled below −5° C.
In addition, the conventional art suggests generation of the non-frozen state using supercooling, but does not suggest the arrangement structure, shape and control of an electrode and a storing space for maintaining the non frozen state.